Theoretical Calculation of Jet Fuel Thermochemistry. 1. Tetrahydrodicylopentadiene (JP10) Thermochemistry Using the CBS-QB3 and G3(MP2)//B3LYP Methods

Abstract

High-level ab initio calculations have been performed on the exo and endo isomers of gas-phase tetrahydrodicyclopentadiene (THDCPD), a principal component of the jet fuel JP10, using the Gaussian G(x) and G(x)(MP(x)) composite methods, as well as the CBS-QB3 method, and using a variety of isodesmic and homodesmotic reaction schemes. The impetus for this work is to help resolve large discrepancies existing between literature measurements of the formation enthalpy Delta(f)H degrees (298) for exo-THDCPD. We find that use of the isodesmic bond separation reaction C(10)H(16) + 14CH(4) --> 12C(2)H(6) yields results for the exo isomer (JP10) in between the two experimentally accepted values, for the composite methods G3(MP2), G3(MP2)//B3LYP, and CBS-QB3. Application of this same isodesmic bond separation scheme to gas-phase adamantane yields a value for Delta(f)H degrees (298) within 5 kJ/mol of experiment. Isodesmic bond separation calculations for the endo isomer give a heat of formation in excellent agreement with the experimental measurement. Combining our calculated values for the gas-phase heat of formation with recent measurements of the heat of vaporization yields recommended values for Delta(f)H degrees (298)liq of -126.4 and -114.7 kJ/mol for the exo and endo isomers, respectively.

JP-10 combustion studied with shock tube experiments and modeled with automatic reaction mechanism generation

“…Zehe and Jaffe [11] studied the thermochemistry of exotetrahydrodicyclopentadiene using composite methods such as CBS-QB3 and the Gx family of methods. Bozzelli et al [12] extended this to all possible radicals formed after abstracting a hydrogen from JP-10 and used a reaction scheme approach to obtain enthalpies of formation for various radicals with approximately 1 kcal mol À1 accuracy.…”

A DFT study on the thermal cracking of JP-10

“…The temperature dependence of the product distribution between C 1 and C 5 was derived and found to be in good agreement with experimental observations. Jaffe et al [26] have performed high-level ab initio calculations to study the exo and endo isomers of gas-phase tetrahydrodicyclopentadiene (THDCPD). The calculated values for the gas-phase heat of formation of Δ f H°(298) are −126.4 and −114.7 kJ mol −1 for the exo and endo isomers, respectively.…”

Characterization and Evaluation of High Energy Hydrocarbon Additives for Paraffin-Fuel Hybrid Rockets

“…Values of standard heats of formation for the 299-molecule test set computed using the G3MP2//B3LYP method have a 5.2 kJ/mol mean absolute deviation with experimental data. This method has been shown to work well for the jet fuel additive JP10 (C 10 H 16 ), which is a strained polycyclic hydrocarbon 20 . For the current study we use the G3MP2//B3LYP method as implemented in the Gaussian software package 21 .…”

“…We first compute ΔH rxn (298) by combining the computed enthalpies of all the reactant and product species determined using the G3MP2//B3LYP method and then equate it with the expression for ΔH rxn (298) using standard heats of formation for all species (e.g., from the NIST Chemistry Webbook database 24 ) except [5]ivyane, which is treated as the unknown. Previously, the bond separation and isomerization reactions were found to work best for JP10 20 . The disadvantage with this method is that the errors associated with all the other reactant and product molecules are additive.…”